MICROBIAL COMMUNITIES ASSOCIATED WITH CRITICAL MINERAL RESOURCES IN HISTORIC MINE WASTE FROM SOUTH-CENTRAL NEW MEXICO

New Mexico has a long history of mining, with hundreds of mining districts across the state, many of which contain inactive operations with historic tailings and waste rock. Because many of the deposits in New Mexico are associated with critical minerals, and metallurgical processing was in its infancy when many of these mines were active, they likely contain substantial metal resources in tailings and waste rock that could be used to support domestic critical mineral demand. However, many of these waste piles have been untouched for decades, which may have resulted in substantial metal mobilization by microorganisms. Furthermore, historic waste piles are a potential non-traditional candidate for a ‘green mining’ approach which relies on microorganisms to mobilize metals through pre-fractured material. We therefore analyzed the composition and abundance of microbial communities from five inactive mine sites in three mining districts in South-Central New Mexico which were mined from deposits that are known to contain critical minerals. rRNA gene and transcript sequencing shows that total and active microbial communities do not contain many of the microorganisms associated with traditional bioleaching consortia, and instead are dominated by organoheterotrophic and inorganic nitrogen-oxidizing populations. Nevertheless, many and, in some cases, most of the rRNA gene sequences in these deposits are from unknown microorganisms, which could include novel metal- and sulfur-oxidizing organisms. We will describe the implications of our results for in situ leaching, and will share protocols and lessons learned in microbiological assessments of these historic waste materials.